1. Field of the Invention
The present invention relates to a control device module for a motor vehicle.
2. Description of Related Art
Control device modules are modules that perform control functions. Control device modules are generally known in a large number of different embodiments and variants. One example of such a control device module is described in published German patent document DE 198 07 215. Although in principle it is capable of being applied to arbitrary control device modules, in the following the present invention, as well as the problematic on which is based, is explained with reference to control devices in the area of motor vehicles, in particular with reference to engine control devices.
Control device modules typically have an electrical control device that is situated in a housing, as well as a plug connector having contact pins via which the control device is capable of being coupled to a cable harness of the vehicle. The electrical components inside the housing of the control device, as well as the contact pins of the plug connector, must be protected from particles, and in particular moisture, from the engine compartment, in order to prevent damage due for example to a short-circuit. For this purpose, the housing of the control device and the plug connector should be fashioned so as to be proof in the coupled state against solid materials, liquids, and gases from the engine compartment; this is typically achieved using seals. However, this tight sealing can be ensured only up to a predetermined pressure difference between an internal pressure in the control device module and an external pressure prevailing in the engine compartment. If the pressure difference exceeds the predetermined value, e.g. as a result of a heating of the air inside the control device, the seals will deform in such a way that an exchange of material takes place between the control device module and the engine compartment. This exchange of material is to be avoided.
A first, generally known, approach to the problem described above provides ventilation of the control device and of the plug connector via the coupled cable harness. Here, the cable harness has gas-conducting strands that are connected at one side to an air volume outside the engine compartment and at the other side to the plug connector of the control device module. The plug connector itself is in turn connected to the internal compartment of the control device via a duct. If, for example, air is collected inside the control device in order to cool it, air can be guided into the interior of the control device from outside the engine compartment through the strand in the cable harness, through the plug connector, and through the duct, until the internal pressure in the housing again corresponds essentially to the external pressure in the engine compartment.
A problem with this first approach is that an adequate ventilation of the control device module depends on the cable harness with the gas-conducting strands. If the cable harness is for example incorrectly installed, this can result in poor ventilation and thus in damage to the control device module.
In a second generally known approach to the above-described problem, a special pressure compensating device is provided for the ventilation of the control device in the control device module. For this purpose, the interior of the housing of the control device is connected to the pressure compensating element by a pressure-conducting duct. The pressure compensating element is typically fashioned as a gas-conducting membrane that is impermeable to solid materials and to liquids. As a consequence, in this second approach the ventilation is carried out via the gases in the engine compartment, which are however filtered through the membrane.
However, this second approach has the problem that the plug connector with the coupled cable harness plug is not ventilated. As a result, in the second approach cable harness plugs must be used that provide a sealing of each contact pin of the plug connector in order to ensure that no gas volume is present in the space between the plug connector and the cable harness plug. The presence of an expanding and contracting gas volume would result in penetration of materials from the engine compartment, in particular moisture. Such cable harness plugs and plug connectors are very expensive to manufacture, and often provide only a partial sealing, particularly after frequent coupling and decoupling of the cable harness plug.